An example of a known canister purge solenoid (CPS) valve is shown in commonly assigned U.S. Pat. No. 4,901,974. While the CPS valve shown in that patent is not a regulated CPS valve, a regulated version is known and includes a pressure regulator disposed between the valve's outlet and the solenoid-controlled valve element. The pressure regulator comprises a diaphragm that is spring-biased away from a seat toward a non-restricting condition, but is selectively positionable relative to the seat to selectively restrict the purge flow to the valve outlet. The pressure regulator functions such that as the intake manifold vacuum changes, the restriction that is imposed on the purge flow by the pressure regulator also changes, but in such a way that the manifold vacuum change has no substantial effect on the solenoid-controlled purge flow. In this way, the electrical control signal that is applied to the CPS valve's solenoid exercises full control over the purge flow substantially independently of changes in the manifold vacuum that is present at the CPS valve's outlet.
Another example of a CPS valve is shown in DE 3802664. While the CPS valve of that patent has a diaphragm-controlled valve between the valve's outlet and the solenoid-controlled valve element, it operates in a diverse manner from the regulated version of the CPS valve of U.S. Pat. No. 4,901,974 in that it deliberately strives to change the purge flow in response to manifold vacuum changes at the valve's outlet.
The present invention relates to a new and improved multi-slope CPS valve. The multi-slope feature refers to the ability of the valve to operate along any selected one of a number flow-rate vs. duty-cycle slopes, each of which defines the flow-rate vs. duty-cycle function for a corresponding intensity of intake manifold vacuum. The presently preferred embodiment of the multi-slope CPS valve of the present invention which will be described in the ensuing Description of the Preferred Embodiment is characterized by a construction and arrangement which is quite cost-effective in relation to the regulated CPS valve referred to above because it can be made by converting a regulated CPS valve by using only a few additional parts.
The foregoing features, advantages, and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which are accompanied by drawings. The drawings disclose a presently preferred embodiment of the invention according to the best mode contemplated at the present time for carrying out the invention.